I have a question about chat bots...?

You want to implement a chat bot that will pass a Turing test? I think you're out of luck on that. It's the Holy Grail of AI programming to do what you're proposing to do. You might get a part of the way using, say, Python's Natural Language Toolkit, but doing the rest (i.e. recognizing humor) is semantic and thus (almost) intractable.